Radio telegraph circuit



April 26, I R BLAlR RADIO TELEGRAPH CIRCUIT Filed Sept. 15, 1929 INVEN TOR.

A TTORNEYJ Patented Apr. 26, 1932 Q as RUSSELL M. BLAIaonNonwoon, OHIO, nssieuon itro. THE onosnni same conronn 1 TION, on CINCINNATI, OHIO, -A CORPORATION on Q1110";

:aAnIo TELEGRAPH oI RcUmi' 4 ,Application filed September 1 s,'*1929. sem mast r l break is reduced, to a very low amount, the 7 power consumed during the non-signalling period is exceedingly small; I I accomplish these and other objects which may be pointed out hereinafter or willbe apparent to one skilled in the art upon read ing these-specifications, by that circuit'and 'farrangement of parts'of which'I shall now describe a preferred embodiment, shown in diagram in thedr awings. o V v The numerall indicates the tuned circuit "of an oscillator or a preceding amplifier,- and is shown as contaln ng avaria-ble condenser. 2

and an inductance 3. 4: is a coupling c'oilto provide radio frequency excitation to the amplifier tube 5, and one terminal is connected to the grid 6. The plate of'thc tube,

indicated at26, is provided with a resonant circuit 7 for-tuning, which comprisesthe 1.

ductance 8 and the variable condenser 9; Thecoupling coil 10, coupled with the inductance v 8 supplies power to the antenna; or may be used for driving a succeeding amplifier,

through the leads 11-and'12.

The leads ofa higholtage sourceof plate potential are indicated at 13 and 14513116 first of which is connected with the filament 15, 3.1 and the grid 6 through the inductance 4;,- the second of which is connected with the plate 26 through the resonant circuit '7. Ai'po tentiometjer having parts 16 and 17 is" shunted across the leads 13 and 14; The central terminal, or variable contactof this potentiome-v ter is connected with thescreen grid 18.

Condensers 19' and 20 shunt the resistance I portion 16, and are so arranged as tobe nor mally closed except wheniopene'd' by the ex-' 7 citation of'thesolenoid and the solenoidis 4.

arranged to beexcited by acurrent-source23* controlled byIthtelegraphici key 24;? The ratio of the two-resistance portions 1 6 andil7;

is adjusted to provide the proper. C; po

tentialonthelscreen grid.i-- o.

leads, 11 and 12., When thefkey is opened;

It will now ah'e seen! howthe key 24 com i trols v the output of :.the circuit having the Y tion 16 of'the potentiometer,vreducingi the 'screen grid ovoltagetofz ero The power outv put'of; the circuit will thus begisubstantially zero; and-the power einputdslight; When, t howcverQ-jthe key is closedythe "solenoid 22g e v op'enszth'e cirouit'sbetween;thejrelay contabts; and the action of} thefresistance portion 16 of thep'otentiometer is to raisethe screen grid:

potential to its ,prr' pervalue; The power? output, ofwthe circuit "thereupon I raises to its a full: value; and a signal is sent, The con denser 19" produces; a slight lag in the fin creasingofthe screen gridpotential and-po er'output, and upontheireopening ofthekey" the condenser 19o2caus'es thepotential to-.dieb out rather than'to be ciitofii'sharply Itfwill" I be understoodthat condensers have some 1 Howeventonak'e the potentia l di'e out more gradually, Imay,if desired; use anadditional' 1 H resistance:251c6nnected between the juncture 301? the resistance portions '16 and '17 of the potentiometer Z and therjunctureiof' the leads J (from condensers :19 and.20'.- :By adjusting the condenserx'ldand theresistance 25j the-rate' ofdecay' oflthe.potentialxonthe screenigrid f" may bemore closely c.ontrolled. The resist- I ance '25 niay-haveifany; desired valuefroni; 0 l

Thus by adjusting i the condenser 19- 7 and/orithe resistance:25aany desired value;

r n enem p e e ah rply ew r n "may be 1 I hi 'w y 7 Ijam ablefio controlkey-thumps; ,Thewave p by making the condenser 19 small and'the resistance negligible, or to stop and start 7 gradually by making both large.

nal lengthas se'ntby. thekey, whereas in the circuit of my invention it is added. This considerably facilitates high speed telegra- It will be clearthat 'modifications in my invention maybe made without departing from the spirit of Having thus describedmy invention, what I claim as new and desire to secure by Letters.-Patent,'-is s i Ina radio signalling system, a transmittiingzicircuit having a screeni-grid amplifier,

a screen gridcircuit, means inducing a screen grid potential, said-means comprising a poi {tentiometer bridging. the power leads of the plate circuit, the screen grid lead being'con- V I nected withithe' centralrterminal thereof, and

screen grid; circuit whereby substantiallyto zero. is r r 2: Inaxradi'oisignall-ing system, atransmitting cizrcuithaving a screen'grid amplifier,

ing connected with the central terminal thereof, and key controlled means for short C11- cuiting'the portion of the potentiometer resistance element in series in the screen grid circuit, whereby the screen grid potential may be reduced substantially to zero, and a radiofrequency by-pass condenservbridging the screen grid circuit whereby the potential changes are made gradual, and a resistance in the screen grid leadto the potentiometer ter- RUSSELL M. BLAIR.

minal.

key controlled meanstor short circuiting the I portion; of the potentiometer: resistance ele- 'mentinrseriesintthejscreenigrid circuit whereby thezscreenzgrid potential may be reduced a seree'n gridcircuit;-means inducing a screen.

grid:potentiahlsaidimeans comprising a potentiometer bridging the power leads of the I plete-circtuQthe screen grid lead being 'con- V 40 nected with the central terminal thereof, and

keycontrolledmansfor short circuiting the 7 portion vofrthe potentiometerresistance. elem'ent series in the screen grid circuit, whereby the screenlgrid-potential'may be reduced substantially to zero, and a radio frequency lay-pass condenser bridging the the potential changes are made gradual. Q

3; In a rad o signalling system", a transmitascreen. grid'circuit, means inducing a screen g'rid potential, said means comprising a pocireuitwherebythe screen tentiome'ter lea-d connected :withthe' central ting' -ci-rcuit having ascreen grid amplifier,'

terminal of; said potentiometer' through a1 l supplementary resistance, and-key controlled- 7 means:fOrshOrt circiuting the portion of said resistance e'lementin series in said screen grid hewreducedf substantially to 'zero.

* 4,111- aradi'osignalling-system, aftra-nsn'iittingicircuit having a screen grid amplifieigsa s'creengrid circuit, means inducing agrid: potential, said means compris-- ing ap otentiometerbrid'ging thepow'er leads grid potential may 7 "f of the plate circuit, the screen grid lead be- V Y 

